1. Technical Field
The present invention relates generally to apparatus and methods for cleaning elongate tubes. More particularly, the apparatus and methods relate to using a lance to spray high pressure water into elongated tubes. Specifically, the apparatus and methods of the present invention relate to guiding a lance into elongated tubes by opening and closing doors supporting the lance.
2. Background Information
Heat exchangers are used for the transfer of heat from one fluid medium to another. One of the fluids passes through a series of conduits, or elongated tubes, while the other passes on the outside of the tubes. During this process, carbonaceous and other deposits form on the interior of the individual tubes. Debris and other dirt collects on the surface of the individual tubes. To maintain efficient operation, it is necessary to periodically remove the tubes and clean their interior and exterior surfaces.
One method of cleaning the interior of heat exchanger tubes includes the progressive insertion of a small diameter tube, known as a lance, into the heat exchanger tube and the pumping of high pressure water through the lance to clean the interior of the tube. The water pressure in a lance may easily exceed 10,000 psi with flow rates in excess of 100 gallons per minute. There are problems inherent in using a lance to clean heat exchangers. For example, it is very difficult to keep the lance from buckling and bending while it is being guided into the tube. A more serious problem, however, is jet reaction from the high pressure stream. Since the fluid is forced through the lance at extremely high pressures (in excess of 10,000 psi) the fluid discharge from the lance tip can frequently blow backward and strike the operators guiding the lance.
One apparatus used to clean heat exchangers supports the rear portion of the lance in an elongated channel member which has an open top. The front end (operating end) of each lance is fed into the tube through a vertical separator plate positioned at the front end of the channel member. The drive means comprises a set of motor-driven friction rollers which engage the lances immediately behind the separator plate. The major portion of the lance is supported in the open channel member behind the drive rollers and the motor. However, in these types of apparatus the lance can be quite long and hard to accurately position as it travels on the channel member. Therefore, improved heat exchanger cleaning technology is desired.